TO_NUMBER(expr[,fmt])
Returns the numeric representation of expr based on the fmt string or the default for expr's data type.
If expr is already a numeric, the value is not converted. If expr is a char value, fmt can be:
| % | Percent sign at right of number |
| $ | Dollar sign at left of number |
| B | Display zero as blank |
| 0 | Display leading zeros |
| 9 | A digit position |
| other | Delimiting character (not leading) |
The default mask is as many nines (9s) as required for the number's precision and scale.
If expr is a date value, the returned numeric represents the number of days since year 0 and the portion of the last day.